The field of the present invention relates to optical scanning systems and particularly to a scanning system capable of successfully reading objects aligned in a variety of orientations. Certain embodiments are especially suitable for use as a fixed scanner such as that employed at a supermarket checkout counter reading bar codes such as those found on consumer products.
For effective and accurate performance, a bar code scanner depends upon focused optics and scanning geometry. Fixed scanners frequently employ a rotating polygon mirror which directs a scanning beam toward a mirror array for generating a desired scan pattern. One type of fixed bar code scanner positions a scan engine in a base with a scan window oriented in a horizontal plane. One such scanning system is disclosed in U.S. Pat. No. 5,073,702, in which a scanning beam is reflected off a mirror array which has a plurality of mirrors arranged in a generally semicircular pattern. The scanning beam reflecting off each of the mirrors has a vertically upward component thereby passing through the window/aperture. Objects to be scanned are passed over the window with the bar codes oriented in a generally downward direction.
In another scanner orientation, the scan engine is housed in a vertical tower with the scan window oriented in a vertical plane. In such a vertical scanner, generally all the outgoing scan beams come out sidewards also having an upward vertical component. Objects to be scanned are passed in front of the window with the bar codes oriented in a generally sideward direction.
In order to produce a successful scan, an object must be oriented with its bar code passed in front of the scan window at an angle which is not so oblique as to prevent a scan line from striking or “seeing” the bar code. Therefore, to achieve a successful scan, the user must position the object with the bar code placed sufficiently close to the desired orientation. The range of suitable plane orientation of the object bearing the bar code is limited by the size of the window and the angle over which the mirror array can direct a scan pattern. Present vertical scanners can scan bar codes oriented on certain lateral sides (i.e., side facing) which face the vertical window, but experience difficulties in scanning faces oriented in a horizontal plane (i.e., facing up or down) or lateral sides opposite the window. Horizontal scanners (i.e., upward facing) are fairly adept at scanning the bottom side but are frequently limited as to which lateral sides may be scanned. The present inventors have recognized that it would be desirable to increase the range of plane orientation readable by a scanning system which would minimize required bar code label orientation, support belt to belt (automatic) scanning, and otherwise provide for improved scanning ergonomics.